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Full text of "Text Book Of Mechanical Engineering"

Solid Forging v.  Welding.                    \ 15

itself quite correctly to the other. One heat should be given for
each of these settings down, and during the third the hole (B) is
punched. Next, the handles are to be welded to the bits, and for
this purpose round rods of sufficient length are scarfed, heated to
welding, and united in the usual manner c, being finished care-
fully in round swages, D. The nose bits are yet flat; they are
therefore rounded by means of atop fuller and bottom swage, as
at E, and, finally, the two half-tongs are riveted together tightly
as at F with a hot rivet, the handles being worked backward
and forward while the rivet is cooling, and also during the
after quenching in water, This method ensures a well-riveted
but workable joint

The student will notice that in the processes of forging two
principal methods are followed, which in many articles merge
considerably the one into the other. These are the forging of the
object (i) entirely from the solid, by drawing down or cutting out;
and (2) the joining of the parts of the forging by welding. The
former is a process of cutting out or carving, the latter of building
up. Figs. 104, 106, 107, and 108 are examples of the first method,
which is the one practised unless the method of welding should be
cheaper, and, as we shall see, is always used if possible in large
objects that have to sustain important loads. Figs, in, ir 3, r 15,
and 116 are cases where the second method is more useful, for in
Fig. r 16 a round bar is attached to work that is easiest forged
from a square bar, and the end pieces in Fig. 112 are manifestly
easier made separately and welded, than they would be by forging
completely from the solid,

Further examples of welding are shewn in Fig. n6a. In each
case A is the work prepared by scarfing or otherwise, and B the
built up article. The Eye may be said to be merely an example
of ornamental welding, for it would be difficult to find a use for it
in practice, The Stud is more commonly met with.; It is prepared
as shewn, by scoring the surfaces to be welded with a chisel; less
pressure will then "be required, the form of the stud will not be so
much distorted at the shoulder, and tjie two pieces are much more
likely to enter into each other.

The next three forgings to be described will be worked in the
* solid' manner, and they will conclude our description of those